Rivers may again decide to give Glen Davis a start in place of Garnett as the Celtics face the lowly Thunder in the opener of a five-game homestand Sunday night.
Boston (55-19) isn't likely to earn the Eastern Conference's top seed, trailing Cleveland by five games with eight to play, but it's tied with Orlando for second place and could certainly use a healthy Garnett (knee) down the stretch.
But Rivers doesn't intend to rush the veteran back into the rotation. The Celtics need Garnett fresh to make a run at their second straight title.
Garnett played a limited role in four games after missing 13 in a row. He was still experiencing soreness after returning and was held out of Boston's 99-93 win over Atlanta on Friday night.
Rivers said Garnett, averaging 15.8 points and 8.5 rebounds for his lowest numbers in 13 seasons, would have been in uniform for a playoff game.
Four of Boston's last eight opponents have losing records, so the Celtics may not need Garnett to secure the No. 2 seed in the East. Oklahoma City (20-52) has the worst record among Boston's remaining foes.
More strong play from Davis would make it even easier for Rivers to keep Garnett on the bench. Davis had 19 points and matched his career high with 12 rebounds against the Hawks.
"We've got a group that believes they're going to win games no matter who's on the floor," Rivers said.
At 6-foot-9 and 289 pounds, "Big Baby" Davis gives Boston's starting lineup more bulk.
Paul Pierce, who starts at the Celtics' other forward spot, has combined for 47 points in his last two games after averaging 8.0 in his previous three contests. He'll be matched up with Thunder star Kevin Durant, who shot just 4-for-13 in a 112-96 loss to Toronto on Friday night.
The second-year swingman was held Friday to 18 points, 7.8 below his season average. He had 17 points on 6-for-15 shooting in Oklahoma City's 96-83 loss to Boston on Nov. 5, and is 0-3 all-time versus the Celtics.
Durant wasn't the only Thunder player who struggled against the Raptors, with their starters combining to shoot 33.9 percent (18-for-53).
Oklahoma City rookie point guard Russell Westbrook continues to struggle with his shot down the stretch of the season. He's averaging 9.0 points and shooting 28.1 percent (9-for-32) over his last three games.
Westbrook shot 4-for-13 and scored 13 points in his first matchup with the Celtics.
Despite the Thunder's shooting woes, coach Scott Brooks wants his team to focus on shoring up its defense. Oklahoma City has lost six of eight, allowing 100.9 points per game during that stretch.
"Defense is two things," Brooks said. "It's a mind-set and it's also helping each other out and we didn't have either one tonight. We have to make sure we get back to that the next couple of games."